The present invention is directed to an apparatus for non-contacting modification of a surface of a glass article by taking a laser beam from a laser, passing it through a sweep device to create a swept beam, deflecting the swept beam by a deflection device to create a labeling beam moving in a desired path and focusing or directing the labeling beam on the glass surface by an objective lens so that the label is created on the glass surface of the glass article.
In laser labeling of articles, an apparatus is utilized in which a beam from a laser is passed through a photographic shutter to a deflection device or means which is controllable in accordance with the particular labeling job by a process computer or microprocessor. The deflected beam is passed through an objective which focuses the beam onto the surface of the article which is to be labeled. Articles of metal, ceramic and semiconductor materials and a multitude of synthetic materials can then be labeled by the laser labeling with letters, numerals, marks, company symbols, and logos or graphic illustrations which are part of the labeling job. The labeling can therefore be executed with an engraving script, fusing script and an evaporation script or by means of discoloration of the surface. The deflection device or means of the known apparatus is composed of a first deflecting mirror for deflecting the laser beam in a first direction such as the x-direction and a second deflecting mirror for deflecting the beam perpendicular to the first direction such as in a y-direction. Both deflecting mirrors are designed as galvanometer mirrors. These galvanometer mirrors are distinguished by a low amount of inertia of the movable parts. At the same time, the deflection device also fulfills the task of a sweep means by means of which the laser beam was swept such as in a horizontal and vertical direction to describe a circle on the surface of the article to be labeled and the sweep means will define the stroke thickness of the labeling device. To this end, the coil for the galvanometer mirrors supplied with the voltage Ux=sin .omega. t for the horizontal deflection and a coil for the galvanometer mirror is supplied with the voltage Uy=sin (.omega.t+.alpha.) for the vertical or y-deflection so that the sweep frequency is referenced .omega., the time is referenced t and the angle of the phase shift is referenced .alpha.. The angle .alpha. is set such that the laser beam describes a circle on the surface of the article to be labeled. The sweep frequencies, which are obtainable with the combined deflection and sweep device, are at a maximum of 100 to 150 Hz.
Given the employment of the known apparatus for labeling, decorating or marking glass, macroscopic splinters will occur in the edge region of the swept laser beam. These splinters have a considerable negative effect on the optical appearance image and in addition lead to injuries under certain conditions.
In order to be able to apply letters, numerals, marks, calibration strokes, company symbols or logos, graphic illustrations and ornamentations to articles of glass in a high-grade quality by means of a laser beam, other ways were therefore sought. One method which is disclosed in German OS No. 31 45 278 uses a non-contacting erosion of material from the surface of an article of glass wherein the laser beam is conducted through a partially absorbing matrix and is divided into a plurality of subbeams in order to achieve a shaped-edge erosion without splintering. The energy available in the laser beam is therefore divided in the beam cross-section and the subbeams can be adapted to a desired erosion. However, a mask must be disposed between the laser and the workpiece with the mask defining the shape of the labeling, marking or symbol. The high flexibility of the apparatus having a laser beam controllable in accordance with the labeling job can therefore not be achieved with this device.